This application claims priority to German patent application no. 10040146.5; filed Aug. 16, 2000.
This invention relates to members of a deep rolling tool used in supporting and locating work rollers.
Prior art deep rolling tools include a housing to which two L-shaped, adjustable roller brackets are attached. On their extreme ends the roller brackets have recesses made to guide cages. These cages are designed for the floating support of the work rollers, in the vertical direction as well as laterally toward the outside. This allows the outside circumferential surface of the work rollers to engage the grooves of crankshaft journals or crank pins for deep rolling of these journals, as described in EP 0 839 607. Work rollers are made of a hard material such as hardened steel, carbide or ceramics.
It is also known that any work to be deep rolled such as crankshafts, is subjected to manufacturing tolerances. In crankshafts, this includes deviations in journal width, misalignment of grooves (eccentricity), deviations in journal spacings and the elongation of the crankshaft itself, all induced by deep rolling. In tools known in the art, the work rollers are supported in their cages in a way allowing them to compensate for these manufacturing tolerances. This capability to compensate is however diminished progressively through their use and the related wear and tear of the tool. With extensive wear a certain xe2x80x9cfixationxe2x80x9d of the work roller inside the cage is experienced, which results in the cage wearing unilaterally, the guiding faces wearing unilaterally, the deep rolling depths varying, and the work rollers themselves wearing faster until ultimately they develop some chipping in their circumferential surfaces. These conditions will accelerate when the deep rolling force is increased. As a result the service life of the deep rolling tools is reduced.
The object of the invention calls for further improvement in the support of deep rolling work rollers in their cages to provide an increased service life for the tools.
The mean selected for attaining this object provides for greater mobility of the work roller in a minimum of one of the two cages in which it floats and, at the same time, for its support on a hard supporting surface. Specifically the support surface is provided by the face of a longish pin fitted in the recess of the cage in which the work roller is guided. It is beneficial to design the pin to be axially adjustable inside the cage, to allow for readjustments with wear. Also, it will suffice to use a pin with a planar face; alternatively, though, the face of the pin may also have a concave depression of moderate depth corresponding to the profile of the work roller.
Another preferred embodiment has the cage divided at its axial center, and a minimum of one of the divided halves flexibly guided in the direction of the width of the journal or crank pin to be rolled. Such mobility is also attained when, e.g., the tool holder is divided over one section of its length, forming two parallel legs, each of which at its extreme end having pocket-shaped recesses for guiding the work roller. A longish pin providing the support surface for the work roller is guided in a minimum of one of the legs. Here again it is intended to arrange for the pin to be axially sliding inside the leg of the L-shaped holder.
The longish pin may have a round, oval or polygonal cross-section. It consists of a hard material, e.g., hardened steel. It is important for the sections of the pin faces that contact the work roller, to have favorable sliding characteristics. To this end the contacting surfaces may be provided with an anti-friction coating.